FIRE Number Calculator

Last reviewed: June 2026

What is a FIRE number?

Your FIRE number is the portfolio size that, at a given withdrawal rate, can fund your annual spending indefinitely. The arithmetic is a single identity:

At a 4% withdrawal rate, 1 / 0.04 = 25 — the familiar “25× rule.” The division form and the multiplication form are the same equation. At $60,000/year and 4%, the FIRE number is $1,500,000. At 3.5%, it rises to ~$1,714,286. At 3%, it reaches $2,000,000. The calculator above recomputes every figure live as you adjust any input.

One important caveat: the FIRE number is a target, not a prediction. Whether a portfolio of that size will actually sustain your spending for a 30- or 40-year retirement depends on investment returns, the sequence of those returns, inflation, and taxes — questions this tool intentionally does not answer. The Safe Withdrawal Rate Calculator handles those questions, with a full depletion simulation.

Where the 25× rule and the 4% default come from

The 4% figure originates from two landmark papers. William Bengen (1994) analyzed U.S. historical market data from 1926 to 1992 and found that a 4% inflation-adjusted withdrawal from a 50/50 stocks-and-bonds portfolio had never been depleted over any historical 30-year period. He called this SAFEMAX. Four years later, Cooley, Hubbard & Walz (the “Trinity Study,” 1998) replicated and extended the analysis using Ibbotson SBBI data through 1995, producing a widely cited table of historical success rates across withdrawal rates and portfolio allocations.

At 4%, a 50/50 portfolio survived roughly 95% of all historical 30-year windows in the original Trinity Study. Later recreations extended through 2009 and 2014 found near-100% success for the same parameters — a difference attributable to bond index choice and additional data years, not a calculation error. The 4% figure is a planning heuristic derived from a specific body of U.S. historical data, not a guarantee. Shorter horizons may support higher rates; retirements of 40–50 years generally warrant more conservative ones. The full evidence — including data-window discrepancies and sequence-of-returns risk — is unpacked in the Safe Withdrawal Rate Calculator.

Lean, Standard, and Fat FIRE — what the terms actually mean

Lean, Standard, and Fat FIRE are informal community planning categories. No authoritative body defines the thresholds; they vary by source, geography, and year:

• Lean FIRE typically describes a deliberately frugal retirement lifestyle, often in a lower-cost location. Annual spending is commonly cited as roughly $40,000 or below — equivalent to a FIRE number around $1 million at 4%. The precise cutoff shifts by source and by what “frugal” means in a given location.
• Standard FIRE (also called Traditional FIRE) covers a moderate middle range, roughly $40k–$80k/year, closer to median U.S. household spending. The label implies neither extreme austerity nor luxury.
• Fat FIRE describes financial independence at a higher spending level, typically cited above $100,000/year. Some sources place the threshold at $150k, $200k, or $300k+. A $100k/year spending goal at 4% implies a $2.5 million FIRE number; at $200k it implies $5 million. The label is relative and geography-dependent.

The tier defaults on this calculator are editable starting points, not classifications. A spending level that qualifies as “Fat” by one community's standard is baseline necessity in a high-cost city. Enter your own realistic retirement spending and read your own number directly. The tiers provide context — not a verdict.

Why spending — not income — determines your FIRE number

The FIRE number depends entirely on what you plan to spend in retirement, not what you earn before it. A high income that is fully consumed leaves the same FIRE number as a lower income with identical spending. This is the core of the framework: cutting spending has two simultaneous effects — it lowers the FIRE target directly and raises the savings rate that closes the gap. Income determines how quickly you reach your number; spending determines what that number is.

Enter your realistic expected retirement spending — including housing, food, healthcare, and discretionary expenses — not your current gross income. If your spending will change materially in retirement (mortgage paid off, children independent, healthcare costs rising) use the retirement-era estimate, not today's figure.

What this calculator models — and what it doesn't

This tool answers one specific question: given your spending and a withdrawal rate, how large does your portfolio need to be? That is the full scope. It does not model:

• How long it takes to reach your number. That is a time-to-target question requiring expected return, inflation, and contribution rate. The Coast FIRE Calculator handles it, with a by-age projection and chart.
• Whether this portfolio will actually last. Portfolio survival over decades of withdrawals depends on return sequences, not just a rate assumption. The Safe Withdrawal Rate Calculator runs a full depletion simulation and shows sequence-of-returns risk directly.
• Taxes. The FIRE number is pre-tax. Withdrawals from a traditional 401(k) or IRA are taxed as ordinary income; Roth account withdrawals are generally tax-free in retirement. Factor in your effective tax rate, or treat this as a pre-tax target and plan gross withdrawals accordingly.
• Social Security, a pension, or other guaranteed income. If guaranteed income covers part of your spending, subtract it from the annual spending input. Your portfolio only needs to fund the gap. The Barista FIRE Calculator handles the part-time income case explicitly.
• Portfolio fees. A 0.5% annual expense ratio on a $1.5M portfolio costs $7,500/year. It is not deducted here. Subtract expected fees from your nominal return when using the Safe Withdrawal Rate Calculator's depletion simulation.

These are scope boundaries, not oversights. Every additional assumption is another way the number can be wrong. This tool requires exactly one assumption — the withdrawal rate — and makes it visible and editable. That transparency is the point.

How to use this calculator

Start with your annual spending in the first field — the realistic amount you expect to spend each year in retirement, in today's dollars. Your FIRE number appears immediately. Then explore the withdrawal rate: 4% is the default, derived from U.S. historical data for a 30-year retirement. For a 40- or 50-year early retirement, or to build in a margin of safety, try 3% or 3.5%. The multiplier updates live — at 3.5%, you need ~28.6× annual spending instead of 25×.

The tier comparison below shows how your spending relates to common Lean, Standard, and Fat FIRE benchmarks at the same withdrawal rate. Every tier value is editable — change them to match scenarios relevant to your geography and lifestyle. The matching tier row highlights automatically, labeled as approximate context rather than a verdict.

Once you have your number, the natural next question is “when will I reach it?” Take your FIRE number to the Coast FIRE Calculator, which models the time-to-target path with monthly contributions and compound growth.

Frequently asked questions

Is 25× spending always the right target?

Only at exactly 4%. The multiplier is 1 / rate: at 3.5% it is ~28.6×; at 3% it is ~33×; at 5% it is 20×. The 4% default is a planning anchor from U.S. historical data, not a universal answer. Adjust the withdrawal rate in the calculator to see how your number changes with different assumptions.

Should I include Social Security or a pension?

Enter the net gap — annual spending minus guaranteed income. If you expect $20,000/year from Social Security and plan to spend $60,000/year, enter $40,000 as your spending. Your FIRE number at 4% drops from $1,500,000 to $1,000,000. The Barista FIRE Calculator models the part-time income case explicitly, including a portfolio projection by age.

What if my spending will be different in retirement?

Enter your expected retirement spending, not your current spending. Many planners use current spending as a proxy, but the FIRE number that matters is the one that matches your actual retirement lifestyle cost. If your mortgage will be paid off, healthcare costs are expected to rise, or you plan to travel more, adjust accordingly.

What does “Fat FIRE” actually mean?

An informal community label for financial independence at a higher spending level, typically above $100,000/year — though different sources set the threshold at $150k, $200k, or $300k+. The Fat tier default on this page is $100,000/year as a starting point; it is not an authoritative definition. Adjust it to match what a high-spending retirement actually looks like for your life and location.

Why is there no projection showing when I'll reach my FIRE number?

That question requires expected investment return, inflation, and monthly contribution — assumptions this tool deliberately excludes to keep the focus on setting the goal itself. The Coast FIRE Calculator handles the time-to-target projection with a by-age chart. Find your number here, then model the path to it there.